So ... where are they now? It was a nicer webapp, but no substitute for Keynote. Having worked with ObjJ/Cappaccino, I found it to be a frustrating attempt at working around the browser, rather than an actual solution.
Performance on the web hasn't _really_ been an issue in years. The real issue is bad developers set the bar for web applications very low.
That's poppycock. In terme of performance, you simply can't come close to what native apps are doing. We invest enormous effort in leveraging threading and extremely low cost implementations in native code, even dropping down to NEON/etc where appropriate.
There is room for higher level languages (arguably that's what ObjC is, plus ARC) but JS simply is not a replacement for what native app developers are doing. NaCL is.